kudu Posted October 26, 2021 Report Share Posted October 26, 2021 at WOT my weber only opens about half way. I can with my finger push the butterflies down with little pressure and they’ll open fully but with where the throttle cable is connected it will only go halfway open. about 2 weeks back i did mess with the idler screw and fuel mixture screw to tune it better for the colder weather but haven’t had a problem with them not opening since. Any ideas? (i’m about to pull it off the intake manifold just to have it on the bench and have a better view but thought i may ask while i’m doing that) Quote Link to comment
datzenmike Posted October 26, 2021 Report Share Posted October 26, 2021 I assume you are using the 620's old carburetor bellcrank on the Weber??? This is sized to pull the throttle plate around at least 90 degrees to full open. Using one that is too large would reduce this. Adjust the throttle cable by removing any slack. Quote Link to comment
kudu Posted October 27, 2021 Author Report Share Posted October 27, 2021 okay so i pulled it off and i guess i realized what type of carb this is it’s got primaries and secondaries right(i’m used to dcoe’s and ida’s so this 32/36 is brand new to me). The small lower ones are primaries and the top square ones are secondaries? it doesn’t use the factory bellcrank it uses what i assume is what came with it(i didn’t install this it came with it on). I’ll try switching to the factory bellcrank, but there is a significant scrapping noise when they try to open after the first what i think is the primary opens slightly and it starts to open the other ones it scrapes. Im pulling it apart to diagnose that as right now. Quote Link to comment
datzenmike Posted October 27, 2021 Report Share Posted October 27, 2021 Well wait a minute. The throttle will only turn 1/4 of a full circle or from horizontal (closed) to vertical (full open) Quote Link to comment
Stoffregen Motorsports Posted October 27, 2021 Report Share Posted October 27, 2021 Linkages that are improperly assembled or even bent can bind, causing scraping noises and, obviously, improper function, ie - not opening all the way or sticking throttle. Get yourself an exploded view parts diagram and compare that with how yours is assembled to be sure. There are two bushings and a couple washers that, if installed backwards or in the wrong order, can cause problems. Quote Link to comment
Stoffregen Motorsports Posted October 27, 2021 Report Share Posted October 27, 2021 Here you go - Quote Link to comment
Stoffregen Motorsports Posted October 27, 2021 Report Share Posted October 27, 2021 Linkage part #79 can be substituted for just about any other cable or rod-operated control lever, so if yours looks different, it may not be a problem. Or it could be THE problem. You'll have to decide for yourself. The one in the diagram is a generic piece that usually works with BMW 2002 or Alfa Romeo installations, and it can be swapped out for the stock Nissan cable lever. Quote Link to comment
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